# Presentation: 548548

## Outline

** ****Spacecraft Status (MV)**
** ****Payload Status and Science Highlights (BF)**
** ****SOHO Science Operations (SH)**
** ****SOHO Data System (LS)**
** ****SOHO Science Communication (PB)**
** ****Why keep SOHO going? (BF)**
** ****AOB**

## SOHO Payload Status

## GOLFPI: Alan Gabriel (IAS)

- Instrument is nominal and giving no reason for concern.
- Progressive, expected fall-off in throughput is not worrying, and will not prevent GOLF completing the cycle.
- Continuous observations on red wing since recovery
- rotation of quarter-wave plate would require many hours of real-time commanding
- noise level in red and blue wing very similar
- GOLF team wants to avoid any risk of getting stuck in the middle, therefore continue on red wing
- Reserves: redundant channel validated, but unused.

## VIRGOPI: Claus Fröhlich (PMOD/WRC)

- All instruments (PMOD, DIARAD, SPM, LOI) are nominal.
- Long-term changes of TSI have been re-analyzed.
- With new calibration, the “problem” with the early increase seems to be solved.

## MDIPI: Phil Scherrer (Stanford Univ.)

- Nominal
- Over 58 million exposures since launch (60 million ground life test shutter moves)
- Instrument performance has been continually characterized since launch.
- Changes in MDI Front Window Transmission:  2.3% per year
- changes temperature gradient of the front window (about 2° per year)
- changes focus
- 9 focus positions
- started at 1, now at 4
- changes plate scale
- annual variations a few parts in 104
- jumps caused by changing focus about 0.1%
- important to include these changes in helioseismic analyses (mode identification, leakage matrix)
- Other calibration details such as image distortion, detector misalignment and MTF variation now well characterized and documented.

##   MDI Shutter Performance

- Detected in April 2001 that starting on 12 March 2000 the std dev of the exposure time has grown from 12 s to about 40 s (pre-launch requirements: 50 s)
- Problem started abruptly and has developed slowly since (something stuck in a bearing?)
- Now monitoring this quantity daily to see if anything needs to be done
- Affects magnetic field noise (slightly up), and low degree modes (l=0-3)
- Does not affect l>4 modes

## MDIPI: Phil Scherrer (Stanford Univ.)

- Nominal
- Over 58 million exposures since launch (60 million ground life test shutter moves)
- Instrument performance has been continually characterized since launch.
- Changes in MDI Front Window Transmission:  2.3% per year
- changes temperature gradient of the front window (about 2° per year)
- changes focus
- 9 focus positions
- started at 1, now at 4
- changes plate scale
- annual variations a few parts in 104
- jumps caused by changing focus about 0.1%
- important to include these changes in helioseismic analyses (mode identification, leakage matrix)
- Other calibration details such as image distortion, detector misalignment and MTF variation now well characterized and documented.

##      MDI Front Window Transmission

##   MDI Front Window Temperature

## MDI Focus Changes

## MDI Plate Scale Changes

## SUMERPI: Klaus Wilhelm (MPAe)

- Both detectors near end of calibrated lifetime
- Operating at highest voltage level
- “Campaign-mode” observations with off-limb targets
- On-disk observations only for special events and with express authorization of the PI
- Several years of operation possible, if continued to run in “campaign mode” and careful target selection.
- Mechanisms: nominal, except                                                              E-W telescope drive.
- Pointing in high-current mode                  			            possible with constraints, but no  				 	    raster scans allowed.

## CDSPI: Richard Harrison (RAL)

- Continues to operate nominally 					      with the detector systems showing 					        no signs of degradation above 					              what is expected.
- NIS detector
- progressive burn-in in bright lines, 						which is expected
- gives no cause for concern
- burn-in is carefully monitored and folded into the intensity calibration
- pre-incident NIS calibration well understood.
- post-recovery change in sensitivity and its long-term variation is currently being quantified by comparing with SEM, SERTS and quiet Sun data.

## CDSPI: Richard Harrison (RAL)

- GIS
- Detectors nominal
- Slit mechanism anomaly, still under investigation
- Probably software/timing problem with encoder
- Has existed for a number of years without noticeable impact
- All voltage levels & currents remain stable and well within tolerances.
- All critical instrument temperatures remain stable. Some temperature monitors close to thermal blankets show increases due to expected deterioration of the blankets; this causes no major concern.
- All mechanisms continue to operate satisfactorily.
- The ground system is fully functional and was recently upgraded.

## EITPI: Jean-Pierre Delaboudinière (IAS)

- EIT is nominal and giving no reason for concern.
- EIT instrument has a decreasing response, but understood now and well modeled.
- Two major components
- absorption of EUV by a surface contaminant
- reduction in charge collection efficiency (CCE) in CCD due to EUV induced device damage
- Contamination effect has largely disappeared after SOHO recovery
- CCE loss can be tracked by calibration lamp exp. taken regularly throughout the mission.

## EITPI: Jean-Pierre Delaboudinière (IAS)

- Detector degradation now understood and very well modeled.
- Present exposure times range from 7 sec to 2 min, with the vast majority taken in Fe XII 195 at 12 sec.
- The signal-to-noise ration is still very high.
- Expected that future trends in the loss of sensitivity will continue as seen over the last 3 years.
- This would result in another factor 5-8 decrease over the next 5 years.
- Possible to mitigate this loss through extended CCD bakeouts.
- Even with this loss, reasonable exposure times would still yield sufficiently high S/N as to have minimal effect upon the quantitative science and almost no effect on morphological studies (e.g. CME initiation).

## UVCSPI: John Kohl (SAO)

- UVCS is expected to continue performing at full scientific capability for many more years.
- O VI Detector:
- No significant decrease in efficiency in O VI portion of this detector.
- Ly- portion showed 5 to 10% loss of efficiency on _parts_ of detector at a high voltage of 200 EU
- Voltage increase from 200 to 205 EU in January 2000 restored full efficiency
- Max of 250 EU allows nine additional increases of 5 EU.
- Voltage increase of 5 EU every 1.2 years is expected to keep the efficiency loss at < 5%.
- Ly- Detector:
- Has been turned off since November 1998 because it draws about 50% of the maximum current and has regions of elevated background.
- This problem is NOT related to the mission interruption.
- Still operational and treated as a back-up detector for Ly- observations.

## UVCSPI: John Kohl (SAO)

- All mechanisms nominal, except Ly- channel grating drive, which continues to degrade; use is restricted, but scientific function is redundantly provided by O VI channel grating drive.
- Star observations and Spartan 201 have shown the UVCS radiometric calibration to be stable within <10% for entire mission.
- No flight software changes have been needed.

## LASCOPI: Russ Howard (NRL)

- C2 and C3 are nominal.
- C1 has been lost (Fabry-Perot wedge defect).
- Telemetry of C1 is used by C2, C3, and EIT, greatly enhancing their scientific output.
- No degradation in instrument temperature, voltages, or current draws are seen.

## SWANPI: Jean-Loup Bertaux (SA)

- Periscope motors OK
- H Cells: absorbing power is decreasing (as expected)
- +Z sensor: 85% of initial value
- -Z sensor: 25% of initial value
- continuous calibration efforts

## CELIAS / COSTEP / ERNEPIs: Peter Bochsler (Univ. Bern), Horst Kunow (Univ.Kiel), Jarmo Torsti (Univ. Turku)    

- All three unaffected by mission interruption
- CELIAS
- MTOF/PM, STOF/HSTOF, SEM nominal
- CTOF impaired since October 1996 due to hardware failure in HV supply
- COSTEP
- EPHIN: nominal
- LION: front detectors noisy (since launch)
- partially operational for higher fluxes
- separation of e and p possible during solar events
- ERNE
- Both LED and HED nominal
- Increasing temperatures due to thermal insulation degradation a cause for concern, but recent X-panel heater changes have improved the situation.

## Summary

- VIRGO	- nominal
- GOLF	- nominal
- MDI		- nominal
- SUMER	- nominal1
- CDS		- nominal
- EIT		- nominal

- UVCS	 - nominal
- LASCO	 - nominal (C1 lost)
- SWAN	 - nominal
- CELIAS	 - nominal (CTOF impaired)
- COSTEP 	 - nominal (LION impaired)
- ERNE	 - nominal

- 1 SUMER’s detectors near end of calibrated life and restricted pointing capabilities  campaign mode observations

****** **There are no known limitations which should prevent SOHO from completing an entire solar cycle with almost all of its complement of instruments operating at full scientific capability.

## Science Highlights

**TSI continuity over two solar cycles**
**Continued search for *****g***** -modes**
**Improved precision of solar interior models**
**Rotation rate variations at the tachocline**
**Equatorward migration of zonal flows**
**Helioseismic imaging of the far side of the Sun**
**Helioseismic response to surface events**
**The magnetic carpet**
**Nanoflares**
**Coronal dimming**
**Flows as a function of temperature**
**Low coronal hole temperatures, MHD wave origin of wind**
**Source of solar wind in coronal holes**
**Lower wind speed in low-latitude coronal holes**
**Coronal He abundance**
**Low-FIP abundances enhanced in some parts of coronal streamers**
**Plasma ******** ~ 1 in some streamers**
**Evidence for coronal inflows**
**Coronal waves**

**Evidence for magnetic reconnection occurring for hours after flares**
**Evidence for reconnection inflows**
**Multi-stage SEP acceleration and CME connection**
**Long-period oscillations in polar plumes**
**Confirmation of faster wind outflows between coronal plumes than in them**
**Evidence for reconnection-driven heating in post-CME structures**
**Spectroscopic determination of helical motions, heating in structures trailing CME’s**
**Solar wind source scale inferred to be ~ 1 Mm**
**No short-supershort FIP effect on wind fractionation**
**Over 380 comets discovered, over 75% by amateurs using freely available LASCO data**
**Discovery of a comet, undetected in the visible from UV signature of ice sublimation **
**Discovery of comet’s shadow**
**Deceleration of H flow at heliopause**

** **Over 1100 papers in refereed literature
-  Representing the work of more than 1500 scientists

##   Subsurface Structure of Sunspots

- How can sunspots last for several weeks without flying apart?
- Models: inflows
- Observations at surface: outflows!
- Applying the new technique of acoustic tomography to high quality MDI data provided first images of the thermal structure and flows around sunspots *below* the surface.
- Strong inward flows right underneath the surface
- Sunspots surprisingly shallow: become warmer than surroundings already some 4000 km below surface

**Zhao et al.: 2001, ApJ 557, 384**

##       UV/EUV Spectral Atlas 670 – 1609Å

- Best ever analysis of the ultraviolet spectrum of the Sun from 670 to 1609 Å
- 1100 emission lines identified
- 150 of these had not been recorded or identified before
- Particular improvement for Å
- Atlas contains spectra of the quiet Sun, a coronal hole, and a sunspot.
- Rich source of new diagnostic tools to study physical parameters in the solar atmosphere.
- Important product both for solar and stellar communities.

**Curdt et al.: 2001, A&A 375, 591**

## Inflows in the Corona

- LASCO discovery: inflows at distances of  2 - 4 R
- Speeds: 20 km/s to over 100 km/s
- Mostly decelerated or nearly uniform inward motion
- Inflow rate correlated with the occurrence of non-polar coronal holes and other indicators of nonaxisymmetric open flux.
- Origin?
- Gradual closing-down of magnetic flux dragged outward by CME? Collapsing field lines?
- Key role for balance of Sun’s open magnetic flux

**Sheeley & Wang: 2001, ApJ 562, L107**

##       CMEs: Current Sheets & Flux Ropes

- UVCS, EIT, and LASCO observed a CME on 23 March 1998 that exhibited narrow, extremely hot ***(> 6x10******6******K)*** plasma emitting in Fe XVIII.
- This emission occurred a the expected location of a ***current sheet*** predicted by the model of Forbes & Lin (2000).
- Fe XVIII emission occurs between the post-CME arches on the limb and the CME itself.
- The current sheet predicted by Forbes & Lin has a lifetime and spatial scale that is consistent with the spectroscopic constraints.

##   The Event of 5 November 2001Largest Proton Storm of the Current Solar Cycle 

** **

##     SOHO and Comets 				                  

**    ****SOHO and Comets**** ****	****	****	****	****                  **

- As of 2 Jan 2002, SOHO has discovered a total of 386 comets (LASCO: 385, SWAN: 1)
- Over 25% of all comet discoveries since 1760 come from SOHO.
- Over 75% of the comets were discovered by amateurs in our real-time images freely available on the Internet.
- Studies on dust-production of sungrazers:
- tails straight and narrow
- no evidence for Lorentz force on charged dust
- tails include a major population of sub-micron-sized dielectric grains (most probably silicates)
- UV Spectroscopy of a Sungrazing CometComet C/2001 C2 (SOHO-294)
- Outgassing rate  100 kg/s
- Size of comet nucleus  10 m
- Densities:
- 10,000 particles/cm3 at 4.82 R
- 86,000 particles/cm3 at 3.32 R

**Uzzo et al.: 2001, ApJ 558, 403**

##         Water Production of Comet C/1999 S4 (LINEAR)

- SWAN observed hydrogen coma of comet C/1999 S4 from end of May through mid August 2000
- Obtained systematic set of water production rates for this well documented event of complete fragmentation of a cometary nucleus.
- Total amount of water released:   3.3x109 kg
- Combining the SWAN measurements  with Hubble observations of the last fragements yields estimate for size of comet: r = 375 m
- and thus to estimate of density:         15 kg/m3 (surprisingly low!)

**SWAN observations of Comet LINEAR a month before it disintegrated.**

**Fragments of Comet Linear seen as mini-comets by HST on         5 August 2000.**

**M****äkinen et al.: 2001, Science 292, 1326**

## Synoptic Imaging of the                                  Far Side of the Sun

- Synoptic maps combining observed magnetic flux from the near-side of the Sun with proxy flux from the far-side inferred from sound travel time analysis
- Data: medium-*l* MDI data
- Two-skip helioseismic holography (Lindsey & Braun, Science 2000)
- Updated daily

##          Synoptic Imaging of Active Regions     	on the Far Side of the Sun

- Full sky Ly- maps by SWAN
- Enhanced UV radiation from active regions make interstellar hydrogen glow (“searchlights in fog”)
- CNES sponsored study to make this an operational space weather tool

- April 2001: implemented software that produces synoptic full sky Ly- 3 times a week, in which new active regions are easily identifiable.

## Outline

** ****Spacecraft Status (MV)**
** ****Payload Status and Science Highlights (BF)**
** ****SOHO Science Operations (SH)**
** ****SOHO Data System (LS)**
** ****SOHO Science Communication (PB)**
** ****Why keep SOHO going? (BF)**
** ****AOB**