The Earth's diffuse auroral precipitation is a major source of energy to the ionosphere and plays an essential role in the magnetosphere-ionosphere coupling. The global pattern of precipitation can dramatically change the ionospheric conductivity and electric potential, which in turn influence the magnetospheric convection. Diffuse auroral precipitation therefore provides a strong coupling mechanism between the magnetosphere and the ionosphere (Ni et al., 2016). It is found that the diffuse aurora has a latitude range of 5°-10° and maps to regions from ring current (L ∼ 4) to central plasma sheet (L ∼ 12) (Meredith et al., 2009; Newell et al., 2009). Based on 11 years of DMSP observations, Newell et al. (2009) found that the diffuse aurora constitutes 84% of the energy flux (63% electrons and 21% ions) into the ionosphere during low solar wind driving conditions and 71% of that (57% electrons and 14% ions) during high solar wind driving conditions, suggesting that the contribution of ions with energy from ∼ 0.01 to 30 keV is considerable but still secondary. A recent study by Tian et al. (2020), who statistically analyzed NOAA/POES observations, found that ions with E ∼30-80 keV carry comparable amount of precipitating flux as electrons within the similar energy range. Although they are relevant at different magnetic local time (MLT) sectors, electron and ion precipitation contribute substantially to the global particle precipitation. The diffuse auroral electron precipitation is mainly caused by pitch-angle scattering associated with magnetospheric plasma waves, such as whistler chorus and electron cyclotron harmonic (ECH) waves. Thorne et al. (2010) analyzed satellite wave data and revealed that chorus wave scattering is the dominant mechanism for the precipitation of electron diffuse aurora in the inner magnetosphere. Jordanova et al. (2016) simulated with the RAM-SCB model the electron precipitation by chorus waves during the double-dip storm of October 7-9, 2012, and found the temporal and spatial evolution of modeled precipitating fluxes

• In the post-sunset hours, the plasma restructuring results into independent EPBs • The migrating structure assumed a wave-like pattern possibly related to LSTIDs moving with a velocity of about 650 m/s • The method used to derive PPEFs from the overall ionospheric disturbance is able to discriminate between prompt and delayed disturbance

Gaining insight into the mechanisms that modulate the precipitating fluxes and by that means the energy input into the ionosphere is hence of utmost importance for advancing our understanding of the Magnetosphere-Ionosphere (MI) coupling physics. Although the electron precipitation is considered to be a major source of energy flux into the ionosphere, the contribution of ions to the total energy flux is on average about 15 percent of that of electrons (

Using the equatorial electrojet (EEJ)‐induced surface magnetic field and total electron content (TEC) measurements, we investigated the impact of the sudden stratospheric warming (SSW) of January 2009 on the equatorial electrodynamics and low‐latitude ionosphere over the Indian longitudes. Results indicate that the intensity of EEJ and the TEC over low latitudes (extending up to 30°N) exhibit significant perturbations during and after the SSW peak. One of the interesting features is the deviation of EEJ and TEC from the normal quiet time behavior well before the onset of the SSW. This is found to coincide with the beginning of enhanced planetary wave (PW) activity over high latitudes. The substantial amplification of the semidiurnal perturbation after the SSW peak is seen to be coinciding with the onset of new and full moons. The response of TEC to SSW is found to be latitude dependent as the near‐equatorial (NE) stations show the semidiurnal perturbation only after the SSW peak. Another notable feature is the presence of reduced ionization in the night sector over the NE and low‐latitude regions, appearing as an “ionization hole,” well after the SSW peak. The investigation revealed the existence of a quasi 16 day wave in the TEC over low latitudes similar to the one present in the EEJ strength. These results have been discussed in the light of changes in the dynamical background because of enhanced PW activity during SSW, which creates favorable conditions for the amplification of lunar tides, and their subsequent interaction with the lower thermospheric tidal fields.

The relative contributions of the composition disturbances and the disturbance electric fields in the redistribution of ionospheric plasma is investigated in detail by taking the case of a long‐duration positive ionospheric storm that occurred during 18–21 February 2014. GPS total electron content (TEC) data from the Indian Antarctic station, Bharti (69.4°S, 76.2°E geographic), the northern midlatitude station Hanle (32.8°N, 78.9°E geographic), northern low‐latitude station lying in the vicinity of the anomaly crest, Ahmedabad (23.04°N, 72.54°E geographic, dip latitude 17°N), and the geomagnetic equatorial station, Trivandrum (8.5°N, 77°E geographic, dip latitude 0.01°S) are used in the study. These are the first simultaneous observations of TEC from Bharti and Hanle during a geomagnetic storm. The impact of the intense geomagnetic storm (Dst∼−130 nT) on the southern hemisphere high‐latitude station was a drastic reduction in the TEC (negative ionospheric storm) starting from around 0330 Indian standard time (IST) on 19 February which continued till 21 February, the maximum reduction in TEC at Bharti being ∼35 TEC units on 19 February. In the northern hemisphere midlatitude and equatorial stations, a positive ionospheric storm started on 19 February at around 0900 IST and lasted for 3 days. The maximum enhancement in TEC at Hanle was about ∼25 TECU on 19 February while over Trivandrum it was ∼10 TECU. This long‐duration positive ionospheric storm provided an opportunity to assess the relative contributions of disturbance electric fields and composition changes latitudinally. The results indicate that the negative ionospheric storm over Bharti and the positive ionospheric storm over Hanle are the effect of the changes in the global wind system and the storm‐induced composition changes. At the equatorial latitudes, the positive ionospheric storm was due to the interplay of prompt penetration electric field and disturbance dynamo electric field.