Daytime mid-latitude F2-layer Q-disturbances: A formation mechanism

Abstract

Negative and positive near noontime prolonged (≥3 hours) F2-layer Q-disturbances with deviations in NmF2 > 35% occurred at Rome have been analyzed using aeronomic parameters inferred from fp180 (plasma frequency at 180 km height) and foF2 observations. Both types of NmF2 perturbations occur under quiet (daily Ap < 15 nT) geomagnetic conditions. Day-to-day atomic oxygen [O] variations at F2-region heights specify the type (positive or negative) of Q-disturbance. The [O] concentration is larger on positive and is less on negative Q-disturbance days compared to reference days. This difference takes place not only on average but for all individual Q-disturbances in question. An additional contribution to Q-disturbances formation is provided by solar EUV day-to-day variations. Negative Q-disturbance days are characterized by lower hmF2 while positive – by larger hmF2 compared to reference days. This is due to larger average Tex and vertical plasma drift W on positive Q-disturbance days, the inverse situation takes place for negative Q-disturbance days. Day-to-day changes in global thermospheric circulation may be considered as a plausible mechanism. The analyzed type of F2-layer Q-disturbances can be explained in the framework of contemporary understanding of the thermosphere-ionosphere interaction based on solar and geomagnetic activity as the main drivers.

Mid-Latitude Daytime F2-Layer Disturbance Mechanism under Extremely Low Solar and Geomagnetic Activity in 2008–2009

“…Taking the observed daytime N m F 2 and N e at F 1region heights, the method provides a consistent set of the main aeronomic parameters responsible for the formation of a particular F 2 -layer perturbation. Our analysis [4] of large prolonged (≥3 h) negative and positive noontime F 2 -layer Q-disturbances with deviations of N m F 2 > 35% at Rome has shown that day-to-day atomic oxygen variations at F 2 -region heights specify the type (positive or negative) of the observed perturbations. In that analysis [4], we did not specially separate the 'meteorological' effects, which could take place during the periods in question but were overlapped by geomagnetic activity and solar EUV effects.…”

“…Our analysis [4] of large prolonged (≥3 h) negative and positive noontime F 2 -layer Q-disturbances with deviations of N m F 2 > 35% at Rome has shown that day-to-day atomic oxygen variations at F 2 -region heights specify the type (positive or negative) of the observed perturbations. In that analysis [4], we did not specially separate the 'meteorological' effects, which could take place during the periods in question but were overlapped by geomagnetic activity and solar EUV effects. Therefore, a special analysis is required to identify pure 'meteorological' effects in N m F 2 variations.…”

“…Quiet time F 2 -layer disturbances (Q-disturbances) present a special class of N m F 2 perturbations occurring under magnetically quiet conditions. Their morphology and the formation mechanism differ from F 2 -layer storm effects related to enhanced geomagnetic activity [1][2][3][4]. Such day-to-day N m F 2 variations may be considered in the framework of F 2layer variability [5][6][7].…”

Ionosonde Data Analysis in Relation to the 2016 Central Italian Earthquakes

“…Therefore, besides the geomagnetic activity effects, there are many other sources of foF2 variation. The morphology of the F2-layer perturbations not related to geomagnetic activity (so-called Q-disturbances) can be found in Perrone et al [38] (see also, e.g., [39,40]).…”

Reply to Comments by Lei et al. on the Paper “Poststorm Thermospheric NO Overcooling?” by A.V. Mikhailov and L. Perrone (2020)

“…The retrieved h m F 2 values demonstrated a standard deviation close to the expected inaccuracy of h m F 2 determination. A comparison of the retrieved EUV to observed one as well to satellite neutral gas density observations given by Perrone et al (2020b) provides an absolutely independent check of the method as the observed EUV and neutral gas density have nothing common with the retrieval process. Figure 1 gives a comparison of June monthly median retrieved EUV flux to composite HLα (Machol et al, 2019) and EUVAC model (Richards et al, 1994) variations for the period.The correlation coefficient between the retrieved EUV and HLα variations is 0.978 ± 0.018 being significant at the 99.9% confidence level according to Student criterion.…”