Ring Current Ion Populations during Geomagnetically Disturbed Periods

  • David Robert Forster

Traethawd ymchwil myfyriwr: Traethawd Ymchwil DoethurolDoethur mewn Athroniaeth


Charge exchange is investigated as a source of magnetospheric He+ . Ionic data from the Magnetospheric Ion Composition Spectrometer (MICS) on the Combined Release and Radiation Effects Satellite (CRRES) are investigated during storm and quiet periods. A He+ /He++ maximum is observed at Ring Current altitudes, where particle trapping is relatively stable. A study of ionic number density across the main and recovery phases of geomagnetic storms provides evidence of a recovery phase source of He+ that does not include the other species. It is suggested that charge exchange of trapped He++ ions with exospheric neutral hydrogen is the source of this He + . Cross sections are obtained for the He++ He+ charge exchange reaction. A new population of He+ ions is observed within the drift echo of an injection which occurred during orbit 497 of CRRES, at E/q values not present in the injection. The possibility of this new He+ population having arisen due to charge exchange is discussed, and charge exchange cross sections are calculated for the reaction. The cross sections calculated for these data are larger than those found by previous work, and it is concluded that the observed effect cannot be explained entirely by charge exchange. Solar wind precursors to pseudobreakups are compared to those of substorms. [Tsurutani et al., 2003] gave examples of stormtime periods which did not contain substorm expansion phases. These are investigated for evidence of electron injections at geosynchronous altitude. It is shown that injections did occur during these periods, though generally at lower energy than those with expansions. The injections are attributed to pseudobreakup activity rather than full substorms. Solar wind parameters are compared to injection energy for storms with expansions and without. It is shown that the occurrence of expansions is associated with spikes in solar wind density, though a time lag of up to 20 minutes is required. This is explained in relation to the pressure catastrophe ([Erickson and Wolf, 1980]), whereby some time is required for magnetospheric convection.
Dyddiad Dyfarnu22 Chwef 2012
Iaith wreiddiolSaesneg
Sefydliad Dyfarnu
  • Prifysgol Aberystwyth
NoddwyrScience & Technology Facilities Council
GoruchwyliwrManuel Grande (Goruchwylydd) & Balazs Pinter (Goruchwylydd)

Dyfynnu hyn