# Presentation: 702348

## Ionospheric and Magnetospheric Plasma (and Neutral Density) Effects

***Ionospheric and Magnetospheric ******Plasma (and Neutral Density) Effects***

**David Cooke**
**Gregory Ginet **
**Air Force Research Laboratory**
**Space Vehicles Directorate**
**Hanscom AFB, MA**

***Solar and Space Physics and the Vision for Space Exploration***
***Wintergreen Resort, VA***
***16-20 October 2005***

## We define plasma effects as the result of interactions between the natural space plasma and a particular system, e.g. communications, radar or satellite.
Radio wave reflection and refraction
Radio link scintillation
Satellite drag (a neutral density effect)
Satellite surface charging and materials degradation

There can also be plasma effects due to active on-board plasma systems (but not addressed in this presentation)
Electric propulsion
Electron beams
Tethers

- Radio wave reflection and refraction
- Radio link scintillation
- Satellite drag (a neutral density effect)
- Satellite surface charging and materials degradation
- There can also be plasma effects due to active on-board plasma systems (but not addressed in this presentation)
- Electric propulsion
- Electron beams
- Tethers

***Plasma Effects ******Introduction***

## Plasma EffectsIonosphere

***Plasma Effects******Ionosphere***

**Ionosphere formed by solar EUV/UV radiation...**

**Subject to Raleigh-Taylor instability during day to night transition**

**...****and is an inhomogeneous dielectric**

**POLAR IONOSPHERIC**
**DISTURBANCES**

**EQUATORIAL **
**IONOSPHERIC**
**DISTURBANCES**

**MAGNETIC**
**EQUATOR**

## Plasma EffectsElectron Density

***Plasma Effects******Electron Density***

- Effects HF communications, GPS single and dual frequency,
- radar & geolocation accuracy

## Plasma EffectsScintillation

***Plasma Effects******Scintillation***

- Degrades UHF (SATCOM) and L-Band (GPS) systems

## Plasma EffectsComm/Nav Outage Forecast System (C/NOFS)

- Forecasting Algorithms & Modeling

- Data Exploitation

- Ionospheric               Space & Ground Sensors

**Real-time in-situ and remote sensing data**

**Combination of physics-based and empirical forecasting techniques**

**Space, ground, and modeled data usage for forecasting**

***Plasma Effects******Comm/Nav Outage Forecast System (C/NOFS)***

-  Provide scintillation nowcasts
-  Develop capabilities to produce short (2-3 hrs before onset), medium (4-6 hrs before onset) and long term (24-72 hrs before onset) scintillation forecasts
-   Improved understanding of equatorial ionosphere and scintillation triggers / inhibitors

## Plasma EfectsC/NOFS Payload Description

- _RAM Plasma Sensors_

**Planar Langmuir Probe** (**PLP**)
-   Developed by AFRL/VS (D. Hunton PI)
-   Measures: Ion Density, Ion Density Variations, Electron Temperature

**Ion Velocity Meter** (**IVM**)
-   Developed by Univ. of Texas(R. Heelis PI)
-   Measures: Vector Ion Velocity, Ion Density, Ion Temperature

**Neutral Wind Meter** (**NWM**)
-   Developed by Univ. of Texas(R. Heelis PI)
-   Measures: Vector Neutral Wind Velocity

- _RF Beacon_
**Coherent EM Radio Tomography** (**CERTO**)
-   Developed by NRL (P. Bernhardt PI)
-   Measures: Remote sensing of RF scintillations and LOS TEC

- _GPS Receiver_
**C/NOFS Occultation Receiver for Ionospheric Sensing and Specification** (**CORISS**)
-   Developed by Aerospace (P. Straus PI)
-   Measures: Remote sensing of LOS TEC

- _Electric Field Instrument_
**Vector Electric Field Instrument** (**VEFI**)
-   Developed by NASA/GSFC (R. Pfaff PI)
-   Measures: Vector AC and       DC electric fields

**Notes:**
We still have the magnetometer?  Why not have Mario’s name.

## Plasma EffectsEquatorial Plasma Bubble Modeling

***Plasma Effects******Equatorial Plasma Bubble Modeling***

_**Problem**_**:****  ****Equatorial plasma bubbles (EPBs) cause degradation of communication/navigation signals  **

_**Solution**_**:**
**Derived global climatology (seasonal/longitudinal) using DMSP data; validated with ROCSAT-1 equatorial satellite**
**Developed working 3D model of EPB development**

**Longitude**

**DMSP EPBs  1989 - 2003**

**2D**

**3D**

## Plasma EffectsRe-entry

- Reentry plasma effects on communication and navigation systems
- Air ionization and heat shield ablation generates plasma sheath around vehicle
- Blackout of navigation and communication links
- Reentry plasma is affected by a complex list of variables.
- Vehicle geometry
- Heat shield composition
- Trajectory

**Understanding of the influence of mission design variables is essential for successful tradespace analysis.**

## Neutral Density EffectsSatellite Drag

-   - Maintain catalog of all space objects
-   - Predict satellite positions
-   - Provide Collision Avoidance warnings
-   - Predict satellite reentries
-   - Optimize satellite design

**Thermospheric Cooling**

***Neutral Density Effects******Satellite Drag***

**Notes:**
Atmospheric drag is the dominant and the most difficult force to determine and predict, in the orbit propagation model of low earth orbiting satellites. Satellite drag errors result in degraded accuracy, requirements for frequent updates and inadequate predictions of true positions for catalog maintenance, collision avoidance and re-entry operations. 
The error in operational empirical models had been at the 15% level for over 30 years. The figure at left show the result of density being greater than that predicted by a model. The orbit contracts more than predicted, and the satellite is further along the orbit than expected. The AF wants the error reduced to 5% to carry out the following missions:
a.  Maintain the world’s best catalog of all orbiting objects
b.  Ensure reconnaissance satellites with very narrow field of view sensors meet their mission
c.  Provide collision avoidance warnings.  AFSPC has the responsibility for providing Collision Avoidance warnings for the International Space Station. This is a very important issue for AFSPC and NASA right now. Improved neutral density data will be a key ingredient in improving this capability.
d.  Predict when satellites will reenter.

## Neutral Density EffectsModeling

- _Problem_: Atmospheric density variations due to geomagnetic storms degrade AFSPC satellite tracking capability

- _Solution_: Develop data-driven first-principles models to replace current operational empirical models for satellite orbit prediction

-  **Empirical model IOC at NORAD 2005**
** ****Improvement to 5% but still...**
-  **Does not meet operational requirements**
** ****Incapable of characterizing storms**
** ****No forecast capability**

**Frank Marcos, et al.**
- High-Accuracy Satellite Drag Model
- (HASDM)

***Neutral Density Effects******Modeling***

**Large storm-induced variations**

## Plasma EffectsMagnetosphere 

- Plasma sheet & ring current

- Outer zone electrons

- Aurora

- Inner belt protons

***Plasma Effects******Magnetosphere****** ***

## Plasma EffectsSatellites 

**Single event effects (SEE)**
**(ions > 40 MeV)**

**Dielectric charging**
**(electrons > 0.2 MeV)**

**Surface charging**
**(electrons 5-50 keV)**

**Total Dose**
**(> 5 MeV p+, > 1 Mev e-)**

**Ionospheric drivers**
**Optical backgrounds**

**Cosmic rays**

**Solar energetic particles**

**Space plasma**
**(and electromagnetic fields)**

**Trapped energetic particles**

**keV**

**GeV**

***Plasma Effects******Satellites****** ***

_**Population**_

_**Hazard**_

**Nuclear Detonation**

- Solar Eruption

- Solar Cell Degradation

- Charging Damage

## Plasma EffectsExample: Solar Array Breakdown 

**Negotiations Under Way For Tempo 2 Settlement    ****___________________________________**
*Space News, August 4, 1997*

**Solar**
**Array**

- Solar cell failures on TEMPO 2 GEO communications satellite
- New failure mode discovered moving from 40 to 100 V arrays
- Charging of spacecraft leads to discharges between the arrays and the space plasma
- Subsequent Kapton pyrolosis leads to self-destruction of the 100 Volt arrays
- Impact on finished, unlaunched satellites currently under investigation

***Plasma Effects******Example: Solar Array Breakdown****** ***

## Plasma effects on materials...

- M. Meshishnek

## Plasma EffectsNASCAP-2K

**AFRL – NASA-SEE partnership effort **
**Spacecraft charging and plasma interaction model **
**Supercedes previous NASA – AF charging codes **
**Non-linear finite elements with continuous electric fields**
**Time dependent PIC and steady state plasma algorithms for self-consistent sheaths, wakes, and plumes**
**Nested Cartesian grids plus local adaptive mesh **
**Object tool and import from 3****rd**** party CAD tools**
**Version 3.0 for LEO & GEO released Jun 05**

**Object ToolKit and GEO charging**

**EP thruster plume effects**

**C/NOFS potential scheme**

***Plasma Effects******NASCAP-2K***

***NASA-AF Spacecraft Charging Analyzer Program – 2000 ***

**NASCAP2K Model  **
**of  STEREO**

## Plasma EffectsCharge Control Technology

**Ion Proportional Surface Emission Cathode**
**Goal:  **Passively emit electrons in proportion to ion current
- Surface emission cathode employs field emission at metal-dielectric-vacuum interface
- Plasma ions enhance the electron emission by maintaining the positive space charge in the substrate, eliminating need for gate
**Status:** In lab development

**M.W. Geis and S. Deneault**

**CCS-II: Xenon plasma – 8 yr @ 0.1 A; 13 Kg charged**

**CCS-I: Xenon plasma – 1 yr @ 0.02 A; 20 Kg, 7 boxes.**

**Charge Control System - II**
**Goal:  **Develop an easy to integrate plasma emission source for charge control.
- Mitigate GEO charging
- Control active spacecraft potential
**Status:** Prototype in lab testing.
**.**

- 35% reduction in weight
- 8X longer lifetime
- 1/3 complexity

**Notes:**
	On the left is a schematic drawing of a surface emission cathode as it might be used in vacuum. The electrons are emitted from the gap between the cathode electrode and the glass or diamond substrate.  Ions from the plasma in the space environment are shadowed from the emitting area by the cathode electrode.  The ions will enhance the electron emission by maintaining the positive space charge in the substrate. 
	The graph on the right demonstrates the self biasing properties of these cathodes.  Once the positive space charge is established with the gate electrode.   The gate voltage can be reduced to zero and the cathode will still emit electrons into vacuum as long as there is a positive electrode in vacuum to collect the emitted electrons.  At 75 s the gate voltage was reduced to zero and the cathode continues to emit electrons.  When the cathode is illuminated (120 s), photo generated electrons in the diamond neutralize the positive space charge and the emission is substantially reduced.  This shows that the emission is not the result of a plasma.   Light is not expected toaeffect the emission from glass substrates as it does with diamond.
	The diamond cathode was operated at a pressure of ~ 5x10-8 Torr.  The emission current is ~ 1x10-4A, the anode voltage is 1100 V, and the current density was calculated assuming a cathode with cathode electrodes spaced 20 μm apart.

## Space Plasma EffectsDifferent Plasma Environments

***Space Plasma Effects******Different Plasma Environments***

## The Lunar ElectrosphereThanks to John Freeman

**The Moon is enveloped with a sheath of photoelectrons**** **
**Observations from Apollo SIDE and CPLEE instruments**
**Day-side: surface potential about + 10 volts due primarily to photoelectrons,  N****≈10****4****/cc within 20cm of surface, few m total height ****(*****Freeman et.al., JGR, 1973*****)**
**Terminator: surface potential of order -50 volts or higher due to energetic electrons from Solar Wind (*****Benson et.al., 1975)***
**Night-side: surface potential = -100 volts or higher in the plasmasheet. (*****Reasoner and Burke, 1972*****)**
**Possible hazard to equipment with exposed potentials**
**Water vapor events.  **
**Observed on several occasions (*****Freeman et.al., 1973)***
**H****2****O****+**** clearly identified**
**Source of events remain unidentified**
**Dusty Plasma**
**Dust raised by impacts, activity, auto-levitation becomes photo-charged and suspended against weak gravity. (*****Stubbs et.al, 2005*****)**
**Potential contamination source**

## Plasma EffectsSummary

- The space plasma environment can affect systems in many ways
- Radio wave reflection and refraction
- Radio link scintillation
- Satellite drag (a neutral density effect)
- Satellite surface charging and materials degradation
- Regions of most concern for the Vision of Space Exploration:
- Earth's magnetosphere and ionosphere
- The solar wind

## Backups

## Space Environment Hazards

**Space Environment Hazards**

_**Space Particle  Hazards**_
**Radiation degradation and electronics upsets**
**Surface and internal charging / discharging**
**Surface sputtering/contamination**

_**Ionosphere/Neutral Hazards**_
**Comm/Nav link degradation and outage**
**Surveillance clutter**
**Satellite Drag**

_**Direct Solar Hazards**_
**Radio, optical and X-ray interference**
** ****Solar energetic particle degradation and clutter**