On the Pre‐Magnetic Storm Signatures in NmF2 in Some Equatorial, Low‐ and Mid‐Latitude Stations

Abstract In this paper, the ionospheric quiet‐time disturbances otherwise known as Pre‐Magnetic Storm Signatures (PMS) have been studied using F2‐layer peak electron density (NmF2) data obtained from 12 Digisonde/ionosonde stations distributed across equatorial, low and mid‐latitudes. The datasets used spans years 2010–2012. Results study reveals strong PMS in NmF2 with percentage deviations (ΔNmF2) ranging −91% to 500% at mid‐latitudes, maxima occurring equatorial region. Significant effects on height of (hmF2) were also observed, they are correlated variations particularly station during PMS. duration a is found be 12–48 h. Although, it was difficult state clearly connection between geomagnetic storm that usually follows within 24–48 h; but hmF2 responses quite similar those observed storms. A slight increase Solar‐wind‐plasma speed (>20 km/s) occur under southward IMF‐Bz, moderate aurora activity (AE 114 560 nT) quiet ring current (Dst >−10 nT). Therefore, pertinent consider certain threshold indices (AE, AL, AU) addition Dst, ap, Kp definition geomagnetically day. This may eliminate ambiguity explaining variability occurs few days before Sudden Commencement (SSC).