Radiation Belt Storm Probes Mission and the Ionosphere-Thermosphere RPSP SWG Meeting June 2009

Two Overlapping Parts of the Same System

Background NASA’s Living With A Star program’s Radiation Belt Storm Probes (RBSP) is one part of a comprehensive set of missions needed to fully understand geospace. Although the ITSP mission is no longer actively being considered it is vital that we continue to recognize RBSP assets relevant to IT science when formulating IT measurements for the early part of the next decade. In conjunction with LEO and/or ground-based observations of ionospheric particle populations and fields, RBSP offers an opportunity to conduct ionosphere- magnetosphere coupling studies. Given the base-lined RBSP mission, the questions are : How can the IT community contribute to the RBSP science goals, and conversely, does RBSP provide measurements that will provide useful inputs to IT studies or planned IT missions?

Middle Latitude Density Plumes Many more drainage plume events have now been identified.

Foster et al, JGR, 2005 Plasma from below 40 degrees magnetic latitude is transported poleward and eventually across the high latitude regions. The sharp ionospheric density gradients have consequences for communications. The expansion of the polar convection pattern can transport middle latitude plasma to high latitudes. Modification of convection by ring current and ionospheric conductivity changes can produce Sub Auroral Ionization Drifts (SAIDs) and Sub Auroral Polarization Streams (SAPS). Inner Magnetospheric Electric Fields GPS TEC data Dusk effect

Low- mid-latitude global-varying E-Fields play significant roles in rearranging ionospheric plasma. Need E measurements to separate E field effects from the ionospheric effects of storm-generated atmospheric winds October 30, LT CHAMP (TEC above 400 km altitude) Ionospheric Density Changes During Storms Mannucci et al., GRL 2005

Can use DMSP Thermal H + to Identify Plasmapause 840 km H + from RPA Drift Meter (O+ is actually dominant) Sharp mid-latitude decrease with latitude – plasmapause field lines in ionosphere. PP defined as where H + gradient terminates. Low latitude electron precipitation boundary from SAMPEX is red line. PP H+H+ pp Good PP correlation with simultaneous IMAGE UV measures of plasmapause field lines.

Correlations with Radiation Belt Electron Changes 72 days in 2001 Mapped DMSP Plasmapause, inner edge of SAMPEX radiation belts electron fluxes, and SAMPEX microbursts (~1 sec relativistic electron bursts) move together with Dst. In lieu of ionospheric H + measurements, mid-latitude trough gradients in topside ionosphere (where H + is dominant) from electron density measurements in situ or remotely from GPS measurements can measure PP location. EMIC inside PP scatters, whistler chorus outside PP energizes PP Daily ave. PP

RBSP Inputs to I-T Studies Electric Field measurements: Middle-, low-latitude ionospheric dynamics, SAPS (Sub-Auroral Polarization Stream), drainage plumes. Ring Current Populations: Ionospheric heating particularly at middle latitudes, E field shielding. B field: Field-line configuration for ionosphere-magnetosphere coupling. Energetic Particle Precipitation – Direct production of ionization: Trimpi, other I-T Effects??? (new discoveries perhaps) Plasmasphere densities: Ionospheric coupling, plasmasphere refilling. Plasmapause measurements: Source of ionospheric troughs and localized ionospheric heating. Others?

I-T Inputs to RBSP Science Electric Field measurements (radar or satellite ion drifts): Complements RBSP E fields with increased L-LT coverage. Ionospheric ion composition: provides source of ions measured by RBSP. Ionospheric density morphology: origin of E field structures; with modeling, enhances knowledge of plasmasphere structure. Ionospheric mid-latitude trough structures – provides global scale perspective of plasmapause topology. Ionospheric Conductivities – crucial to understanding E fields Others? STOP

Subauroral ion drifts (SAID) are latitudinally narrow regions of rapid westward ion drift located in the evening sector and centered on the equatorward edge of the diffuse aurora. Observations of SAID as identified by the ion drift meters on the Atmosphere Explorer C and Dynamics Explorer B spacecraft are utilized to determine their effect on the F region ion composition, their relationship to the mid-latitude trough, and their temporal evolution. At altitudes near the F peak a deep ionization trough is formed in regions of large ion drift where the O+ concentration is considerably depleted and the NO+ concentration is enhanced, while at higher altitudes the trough signature is considerably mitigated or even absent. SAID have been observed to last longer than 30 min but less than 3 hours, and their latitudinal width often becomes narrower as time progresses. The plasma flows westward equatorward of the SAID and becomes more westward as invariant latitude increases. Poleward of the SAID, the flow is, on average, westward throughout the auroral zone in the evening, while near midnight it becomes eastward. Southwood and Wolf. Dusk side plasma ions penetrate more deely. Dominate plasma sheet pressure and generate Region 2 current. Electrons dominate auroral conductance enhancement. Thus low conductance band between eqwd edge electron precipt and equtwd edge of Region 2- so strong electric fields are expected