# Presentation: 252751

## International Solar Terrestrial Physics Program

- Wind
- SOHO
- Polar
- Cluster
- Theory & Ground Based

**International Solar Terrestrial Physics Program**

- Fresh Perspectives on the Complexities of Geospace Dynamics

**Notes:**
This presentation, by request, addresses only Polar, Wind and Geotail science objectives during the coming five years.

## Fresh Perspectives: evolving orbits

- Polar becomes an equatorial mission

- Geotail observes in tail and heliosphere

- The orbits aren’t what they used to be ...

- Wind continues its tour of the near earth heliosphere

## Evolving orbits: Wind

**Notes:**
Projections onto the ecliptic plane in GSE coordinates of the future trajectories of the WIND spacecraft.

The left one, which the spacecraft is presently pursuing, constitutes several “mini-stereo” orbits in which the spacecraft reaches an apogee of ~330 Re.

The rights one is an “earth return” orbit in which with spacecraft explores the interplanetary medium up to 400 RE and the magnetotail up to about 300 Re.

## Evolving orbits: Wind

- Extension of WIND’s 2nd Distant Prograde Orbit (DPO)
- Earth Return Trajectory
- April 2003-April 2005

- WIND Earth Return Trajectory
- 3rd Distant Prograde Orbit
- Dayside DLS
- April 2005 - November 2006

**Notes:**
Projections onto the ecliptic plane in GSE coordinates of the future trajectories of the WIND spacecraft.

The left one, which the spacecraft is presently pursuing, constitutes several “mini-stereo” orbits in which the spacecraft reaches an apogee of ~330 Re.

The rights one is an “earth return” orbit in which with spacecraft explores the interplanetary medium up to 400 RE and the magnetotail up to about 300 Re.

## Evolving orbits: Wind

## Evolving orbits: Polar

- The apogee of Polar has drifted towards the equator and will provide key insight into the nightside (Fall) and dayside (Spring) magnetosphere by observing in those regions for many hours per orbit.

**Notes:**
During recent years, the apogee of Polar has drifted towards the equator in such a way that during Fall (Spring) periods, it is located in the low-latitude night side (day side) at a distance of about 7 Re from the Earth. 
This allows an excellent opportunity to observe the night side magnetosphere over long periods of time during the Fall seasons.  In many ways, Polar is now moving into a position in its orbit that makes it like the original "EQUATOR" spacecraft envisaged for the "OPEN" program..
Polar makes observations of the plasma sheet midway along auroral field lines between the ionosphere and the equatorial plasma sheet. In principle, Polar "scans" through the auroral field lines during a substorm time scale, as magnetic field lines attached to it at different times sweep considerable distances in the equatorial regions. In conjunctions with auroral zone ground stations or low altitude spacecraft, this observational geometry provides measurements of the magnetic field-aligned propagation of the substorm disturbances. Furthermore, the radial propagation can also be addressed by studying relative timing of the substorm disturbances on the Polar field line and at a geostationary spacecraft location.

## Evolving orbits: Geotail

- Geotail has now used up its propellent and the apogee is now drifting
- slightly as shown by the orbits in successive years in January.

**Notes:**
After two years in a deep tail orbit, the apogee of the equatorial
Geotail spacecraft was first reduced to 50 Re in late 1994 and then to
30 Re in early 1995. It has continued in a 10 (now 9) by 30 Re
equatorial orbit with a minimal shift of the apogee of roughly 15
degrees per year in intertial coordinates. In this orbit Geotail
traverses the very interesting equatorial plasmas sheet where
comparisons with Cluster, Wind and Polar will be important.

## Evolving orbits: Fresh perspectives on the nightside

- Polar remains at the same local time for several hours providing good probability that another spacecraft will be located near the same sector during substorm periods.
- Such conjugate observations allow studies of the radial propagation of substorm disturbances such as particle injections and magnetic field dipolarizations.

**Notes:**
Polar is now providing measurements of the inner magnetosphere similar to an equatorial spacecraft. The main difference between Polar and geostationary spacecraft is that Polar remains in the same local time sector for several hours providing good probability that another spacecraft, such as Wind or Geotail, will be located near the same sector during substorm periods. Such conjugate observations are important for studies of the radial propagation of substorm disturbances such as particle injections and magnetic field dipolarizations.

## Evolving orbits: Fresh perspectives on the dayside

## What we have learned: Selected accomplishments  

- Observations by WIND/Waves and SOHO/Lasco show that the shock front trajectories of colliding CMEs are altered.
- Direct observations using each of the ISTP spacecraft have extended our knowledge and understanding of collisionless reconnection phenomena.
- First direct measurement of E parallel and the associated acceleration by solitary wave structures.
- Poynting flux measured above the E parallel region at edge of plasma sheet and pointing down the magnetic field with sufficient energy to account for all auroral phenomena
- Placement of the cause of substorm onset (auroral brightening) in the near plasma sheet and observation of plasma braking prior to onset
- Discovery of very high energy ions (MeV) in the cusp.

**Notes:**
Reconnection:  Considerable interest and controversy in the physics community presently attaches to the phenomenon of magnetic reconnection, both collisional and collisionless.  Wind, Polar and Geotail have provided experimental evidence bearing on this.  Oeroset, Phan and Lin (2000) have used Wind and Geotail to simultaneously detect reconnection at the dayside magnetopause.  An interplanetary example of reconnection has been described by Farrugia et al (2000) and the interpretation of Polar observations in the diffusion region is being completed.  This all adds up to considerable progress in a fundamental field.

## What we will learn that is new:

- Why does significant energy flow to the ionosphere when it does: Substorms vs Pseudo breakups?
- Where do substorms originate:        8 Re or 25 Re?
- Does the prestorm plasma sheet influence the intensity of the following storm?
- Are flow bursts related to low latitude auroral zone substorms, polar cap boundary auroral intensifications or both?

**Notes:**
Although Geotail has demonstrated that reconnection typically occurs near 25 Re at the time of a magnetospheric substorm,  controversy continues over whether this reconnection is the initial cause of a substorm. Some workers contend that the substorms begins closer to 8 Re due to a current driven or ballooning instability and downtail reconnection follows shortly thereafter. In the fall season, the Geotail, Cluster, and Polar spacecraft will be in an ideal position to answer this question. Geotail will make perigee passes through the midnight equatorial region near 9 Re while the Cluster spacecraft make north/south cuts through the equatorial plasma sheet near 20 Re. Polar apogee will be appoaching the equator where it will serve as the Equator spacecraft never available to ISTP. This Polar apogee will also be near midnight where it can provide a third data point. ACE and Wind will monitor the upstream interplanetary conditions.
These magnetosphere spacecraft will be able to measure flow bursts and magnetic field dipolarizations that are associated with substorms, and determine their timing relative to substorm onset. Such measurements should make clear where the substorm begins and what instability is the cause of this most important magnetospheric event.
The figure shows Polar locations (triangles) at various substorm onsets with respect to a model magnetic field configuration. The yellow and blue shadings indicate the plasma sheet and radiation belts, respectively, prior to the substorm onset. Red shows the expanded plasma sheet following the substorm onset. Magenta indicates the substorm-injected particle population. The bottom panel shows the event locations mapped along the magnetic field line in the equatorial plane. The black curves correspond to a 10-minute interval of the Polar orbit.  These substorm onset events, identified during the Falls of 1999 and 2000, are being compared with GOES, Los Alamos geostationary, and IMAGE spacecraft results.  Future comparisons with Geotail ill also be possible.

## What we will learn that is new:

- How and when is auroral zone energy transmitted to low altitudes?
- Under what conditions does the ionosphere dominate the solar wind as a magnetosphere plasma source?
- What is the spatial and temporal coherence of ion outflow?
- How much oxygen escapes from the magnetosphere? How much is lost to the upstream region?
- How does atmospheric composition vary as a result of solar UV flux variation?

**Notes:**
As Polar moves toward lower latitudes the imaging discoveries do not stop.

 Far ultraviolet remote sensing from satellite platforms is a powerful technique for studying thermospheric composition on a global scale, especially for dynamic variations [e.g., Meier, 1991, and references therein].  FUV emission brightness is related to the compositional state of the thermosphere.  Therefore signatures of thermospheric dynamics can be obtained directly from disk 1356 Å and LBH images of the dayglow.  Both have the same electron impact excitation source, and their ratio varies directlywith the O/N2 ratio [Strickland et al., 1995].
The new imaging perspectives provide the opportunity to investigate mechanisms for solar influences on the terrestrial environment. Among the more notable are the ability to determine variations in the global atmospheric O/N2 ratio, the ability to study equatorial “arcs” and to measure variations in thermospheric composition associated with tides.  
When studied at low latitudes, the O/N ratio and its variations provide a reality check for models of the thermosphere.  Additionally, at mid-latitudes the O/N2 ratio can be drastically altered during strong geomagnetic activity, providing a clear example of solar-wind magnetospheric interactions producing effects reaching into the atmosphere.  The O/N2 ratio also has less dramatic tidal variation which are little studied.  
Equatorial arcs are an anomaly appearing after sunset and represent an enhancement in total electron content. 

## What we will learn that is new:

- What is the relative importance of the internal and external sources to magnetospheric energetic particle populations?
- What is the cause and effect of solitary wave structures on auroral particle acceleration?

**Notes:**
Perhaps the most compelling application of the comprehensive electric and plasma wave receivers has been toward the study of solitary wave structures. Solitary structures are narrow, intense electric fields (up to 100 mV/M or more) that converge or diverge depending on whether they represent ion or electron phase space holes. Shown to be the actual source of the phenomenon known as “broadband electrostatic noise”, the wave fields of phase space holes are some of the largest in the magnetosphere and are systematically present in particle acceleration regions with sources of free energy such as the auroral zone, the plasma sheet boundary, the bow shock and the cusp [Bale et al., 1998; Ergun et al., 1998]   Polar has observed electron holes in the magnetosphere at low and high altitudes along auroral field lines [Mozer et al., 1997; Cattell et al., 1998; Franz et al., 1998; Bounds et al., 2000] and along field lines associated with the plasma sheet boundary layer and high altitude cusp [Catell et al., 1999; Tsurutani et al., 1998; Franz et al. 1999].

## What we will learn that is new:

- What role does turbulence play at the boundary layers between solar and magnetospheric plasmas?
- What are the important processes?  Sub-solar versus high latitude merging? Component versus antiparallel merging? Merging versus current disruption?

**Notes:**
On April 1, 1999 in an orbit moving tailward through the Earth’s magnetotail, the WIND spacecraft observed a 10 hour interval of high-speed earthward and tailward plasma jets. Quantitative comparison with predictions from reconnection theory implies that the high-speed flows are generated by magnetic reconnection and that the two observed flow reversals are indicative of the passage of a reconnection X line.  This provides evidence that distant tail (60 earth radii downtail) rceonnection is large-scale and quasi-steady, as opposed to near-Earth magnetotail reconnection. 

## What we will learn that is new:

- Does the magnetotail begin to break up within 400 Re downstream?

**Notes:**
Pioneer 7 and Pioneer 8 made intermittent observations of the magnetotail as they passed behind the Earth at 1000 and 500 Re in the 1960's. ISEE 3 and Geotail also frequently moved back and forth between the magnetosheath and magnetotail at distances up to 200 Re in the early 80's and 90's respectively. In none of these cases, however, were accurate simultaneous upstream measurements of the solar wind flow direction available. Without such measurements researchers were unable to tell whether (1) a well collimated tail was simply moving to and fro like a wind sock in response to solar wind direction changes or (2) the tail had broken up into many separate filaments. In 2005 ? (and what month?) the Wind spacecraft will pass behind the earth near 400 Re when accurate upstream measurements are available from Ace (and Geotail?). Such measurements will allow distinguishing between the above possibilites and answer an important question about planetary magnetotails.

## What we will learn that is new:

- What is the mesoscale topology of solar wind structures observed at 1 AU?
- How do interplanetary structures seen at 1 AU relate to solar impulsive events and their geoeffectiveness?
- Are there distinct classes of CMEs and what are the geoeffective consequences?

- Jan 20, 2001: simultaneous observations by SOHO/LASCO and WIND/Waves at radio wavelengths show collision of pair of CMEs in the outer corona.

**Notes:**
What is the mesoscale topology of solar wind structures observed at 1AU?
Figure __ shows an example of one of the new spacecraft conjunctions that will occur (Aug 2001) between ACE, WIND and Geotail.  WIND is near apogee in the DPO, ACE is in its L1 halo orbit, and Geotail is in the solar wind near Earth.  Such conjunctions, only made possible by WIND’s wide-ranging orbit, will provide unusual opportunities to determine coherence lengths associated with structures such as interplanetary reconnection layers, interplanetary shocks, magnetic clouds, the heliospheric current sheet, planar magnetic structures, anomalous low-density structures, and shocks internal to magnetic clouds.  		
How do interplanetary structures seen at 1AU relate to solar impulsive events and their geoeffectiveness?
Using information gained from the multi-scale analysis of solar wind structures, WIND experimenters will determine how the structures relate to solar impulsive events and their geoeffectiveness.  For example the structure of magnetic clouds, gained from the multi-spacecraft observations, may lead to a more generally satisfactory global theory of these large interplanetary structures which can be used to map them back to the corona.  The topology of these events may have profound effects on their interaction with the Earth. 
Are there distinct classes of CMEs and what are the geoeffective consequences? 	
WIND/WAVES and SOHO/LASCO can make simultaneous radio and white light measurements of colliding CMEs.  In this way, the precise acceleration profile of CME shocks near the sun can be measured.  This potentially allows access to the region in the high corona where the high speed solar wind is accelerated.  A major question, addressed at the AGU in a special session, is whether or not there is more than one class of CME: fast flare-related events and slow prominence-related events.  Combined WAVES/LASCO observations of colliding CME’s in the upper corona should make important progress in answering this question.  

## What we will learn that is new:

- What is the mechanism that accounts for solar energetic particle acceleration?
- Where do Gamma Ray Bursts originate and why are there two distinct classes of bursts?

- Gamma-ray burst supernova source SN199bw.  The KONUS gamma-ray burst instrument on WIND, along with Ulysses and NEAR, provide gamma-ray burst source localizations.

**Notes:**
What is the mechanism that accounts for solar energetic particle acceleration?
Most people believe that the particles in SEP events are shock accelerated, but there is little agreement on many of the details.  For example, the relationship between CME shock speed/spatial scale and particle acceleration energy/flux is not understood.  ACE and WIND energetic particle measurements will be compared over the spatially varying baseline of large-scale shock fronts to better understand SEP acceleration mechanisms.  Prediction of the size of an SEP event may become possible if the acceleration mechanism is better understood.  This would obviously have major consequences for spaceweather.  

Where do Gamma Ray Bursts originate and why are there two distinct classes of bursts? 
The origin of gamma ray bursts is currently unknown.  Recent evidence suggests that there are two distinct classes of GRBs based solely on their burst duration.  Each probably has a different origin.  Two WIND instruments KONUS and TGRS make fundamental GRB, soft gamma repeater (SGR), and hard x-ray transient measurements that could shed additional light on these and other questions concerning GRBs.  Since the termination of COMPTON GRO and BATSE in June 2000, the WIND data have become even more critical to gamma ray studies.  WIND is an important player in the Interplanetary Gamma Ray Burst Timing Network (IPN), which  consists of WIND, Ulysses, and, until recently,  the NEAR gamma ray detector.  The combination of simultaneous GRB detections from these three spacecraft produced about one precise GRB localization per week accounting for about a third of all GRB counterpart searches and studies.  The WIND-Ulysses-Near interplanetary-length tripod localized GRBs to within several minutes of arc, contributing important data to the fundamental question of the origin of GRBs.  Without NEAR, the IPN can localize GRBs in a narrow plane, with the NEAR leg of the tripod to be replaced about 2002.  The WIND gamma ray detectors play a crucial role as the required third vertex in the long-baseline tripod of the GRB IPN. 

## Status of the assets: spacecraft

| POLAR | WIND | GEOTAIL |
| --- | --- | --- |
| MFE | MFI | MGF |
| EFI |  | EFD |
| PWI | Waves | PWI |
| CAMMICE | EPACT | HEP |
| CEPPAD | SMS | EPIC |
| HYDRA | 3DP | LEP |
| TIMAS | SWE | CPI |
| TIDE |  |  |
| UVI | KONUS |  |
| PIXIE | TGRS |  |
| VIS |  |  |

- Fields and waves

- Particles

- Imaging

**Notes:**
POLAR:  Fully 3D particles instruments with considerable energy overlap between instruments; multi-spectral aurora imaging, high resolution fields ... Polar remains one of the best instrumented spacecraft in the magnetosphere.
PWI operates during prolonged eclipses.
Hope to recover TIMAS by switching to redundant GTM on Polar.  Power supply anomaly resulted in lower sensitivities at the lowest energy settings.
TIDE lost its TOF stop pulse signals, its fine energy and angle resolution allows 60-70% of observations to be separated by mass.
Jury still out regarding future PSI operations ... control of spacecraft potential is desirable but not as critical as when mapping the lobes.
PIXIE operates at lower time resolution ... must look up what it is ...
WIND:  1 of the three instrument packages on SMS has been turned off, does the lowest energy (10-30keV) ion composition distributions.   
Also lost 2/3 of one arm of the 50 meter dipole antenna.   
GEOTAIL:    All seven experiments on Geotail are operating normally nearly 9 years after launch with the following exceptions. The mass spectrometer portion of the LEP experiment and a portion of the HEP experiment failed shortly after launch and the electron gun portion of the EFD experiment stopped working after several years. Automatic range switching on the Geotail magnetometer failed several years ago but the experiment operates normally in a fixed range which has little adverse impact on the science. Geotail has already survived the  longest shadows it will encounter (more than twice the duration the spacecraft was designed for) so there are no foreseeable problems in continuing operation.     

## Status of the assets: data system

- CDHF – completely functional
- SPOF/EOF – completely functional
- Data Distribution – all level zero from WIND/POLAR/Geotail/SOHO/IMP 8
- CDAWeb – >0.3 Terabytes of Key Parameters

- Unique joining of data from _current missions_
- NASA:  ACE, FAST, IMAGE, IMP-8,  Polar, SAMPEX, Wind
- Other US: GOES, LANL
- International: , Geotail, SOHO, Ulysses, Interball, Cluster
- International community of users
- Service mirrored in Europe and Japan as part of NASA’s support for the IACG

## Status of the assets: Theory & modeling

- Global magnetohydrodynamic simulations of the magnetosphere have been very successfully implemented by UCLA, UMD, and Dartmouth to provide a global framework for the ISTP observations from widely separated spacecraft
- Simulations of the aurora, the formation of new radiation belts, and global ionospheric convection patterns have also served to provide closure between spacecraft and ground-based observations and theory

- Issue: although capital has been invested in the simulation codes, present funding is not sufficient to provide the staffing to run these simulations in support of experimental observations

## Status of the assets: Ground based 

- Ground-based observatories have provided observational data for the final link in the sun-earth connections:  energy deposition in the atmosphere and ionosphere.  Examples include global convection patterns and detailed studies of processes underlying auroral dynamics.
- Large observation networks such as Superdarn were the direct result of NSF/NASA collaborations

- Issue: Some needed assets such as Superdarn are aging due to extreme environments.  Will future NSF/NASA collaborations be possible to preserve these capabilities for ISTP and future missions?

## ISTP as a distributed observatory: Fresh Perspectives on the Complexities of Geospace Dynamics

- Well-defined, focused science objectives directly contribute to our understanding of the Sun-Earth Connection.
- The ISTP “event driven” paradigm has expanded allowing more and more studies to be successfully defined and carried out with new and calibrated databases.
- The unique “end-to-end” diagnostic capability of ISTP has been thoroughly demonstrated: CME’s, Solar Wind disappearances, SEP’s, etc.

## Backup slides

## Comparison of the particle instruments on Polar

**TIMAS MEASUREMENTS:**
- Energy Range: 	15 eV/e – 32 keV/q
- Mass Range:	1 – 32 AMU/q
- Angular Resolution:	11.25 x 11.25 deg.
- Time Resolution: 	 2-D: 0.375 sec / 3-D: 3 sec

- POLAR carries the full range of instrumentation necessary to resolve details of the field and particle interactions leading to particle acceleration throughout the inner magnetosphere – TIMAS is an important part of that instrument complement.

**TIDE: 2D 0-500eV ions**

**HYDRA – 3D 2-35 keV/q protons**

**CEPPAD – 3D 20 keV/q - 1 MeV protons**

**CAMMICE:  6 keV/q - 60 MeV ion composition**

**CEPPAD:  >10 MeV protons**

**TIMAS: ****3D**** 300 eV/q - 32 keV/q ions**

## Growth in the Multi-Mission SEC Database