For typical auroral substorm related activity, riometer absorption often results from deposition of 10-20 keV electrons at km. Such deposition can lead to increased D-region conductivity and enhanced current flows in this region, usually leading to large magnetic variations. However, more energetic electrons can penetrate to lower altitudes and not greatly increase the conductivity of the lower ionosphere. For example, a 100 keV electron would penetrate to km. Significant magnetometer activity would not be expected for particle deposition at such low altitudes.
Further studies are underway to determine the hardness of the electron spectrum during spike events.
Thus, the relationship between dusk spikes and substorms is not clear. However, the the Ranta et al. The level of absorption in dB is given by the color bar. Note that the sharp spike at 0310 UT is confined to the northern half of the array and that both spikes exhibit equatorward drift of the peak amplitudes.