VAB Disturbances

By using 16.5 years of NOAA particle data, a statistically significant correlation between electron bursts and large strong earthquakes of 2 – 3 hours before mainshocks in Indonesia and the Philippines has been reported, see below with Teq the earthquake time and Tpp the electron burst time (see Fidani, 2015).

The parameters used to obtain the correlation are the earthquake position and depth, the electron burst energy, pitch angle, and L-Shell. Earthquake positions are between Indonesia and the Philippines with depths less than 200 km. Correlated electron bursts of E = 60 - 100 keV are outgoing from the Van Allen Belts with a low L-shell range of 1.15 < L < 1.35, with L that provides information about the altitude where the disturbances could have occurred. These correspond to altitude projections ranging between 1,400 and 2,800 km above the earthquake epicenters. The electrodynamics of electrons suggest a possible causal link. In fact, eastward electron drift periods Td depends on energy by

where α(eq) is the equatorial pitch angle which is near 90°. Thus, the electron energies of 60 keV to 100 keV correspond to periods necessary to cover the entire terrestrial longitude of between 10.5 to 6 hours, respectively. The electrons which produced the correlations crossed the satellite vertical detectors in the drift loss cone high offshore the USA and the South America West Coasts around an average of 120° eastwards from the longitudes of Sumatra and the Philippines, about 2 – 3 hours before the earthquake times (see Fidani, 2018). Being so, it can be calculated that a time interval of 2 – 3.5 hours is necessary for 60 – 100 keV electrons to drift 120°. So, if the disturbances which caused electron precipitations from inner radiation belts occurred above the earthquake epicenters in the ionosphere, they anticipated the earthquake times by 4 – 6.5 hours.

Regarding the physical link, CIEN magnetic detectors were able to record strong magnetic pulses hours before the mainshock. The pulse frequency of 1 to 10 Hz, was similar to the observations made in other countries and resulted in being in resonance with the bouncing motion of electrons at detected energies by NOAA satellites. These results support the hypothesis that there could be electron pitch angle disturbances due to magnetic ULF signals from the ground.

Finally, the whole process can be described in the picture above. From the pitch angles information, electrons of detected bursts were precipitating, which means that their bouncing point altitudes were lowered during disturbances at earthquake epicenter longitudes. Although, lower mirror point altitudes above Indonesia and the Philippines were not sufficient to cross the NOAA-15 satellite which has an altitude of about 800 km. However, given the eastward drift of the electrons and the asymmetry of the geomagnetic field, the crossing between the electron motions and NOAA orbits was possible high offshore of the USA and the South America West Coasts. In fact, at these longitudes, the electron mirror point altitudes have to have gradually touched the satellite altitude and gone lower. Further drifting eastwards, electron mirror point altitudes have to have gone lower and lower up to less than 100 km, which is the atmospheric altitude. Doing so, they were absorbed in correspondence of the South Atlantic Anomaly, about 1 - 2 hours after the crossing of NOAA-15 satellites where a part of them was detected. In this sense, they were called precipitating electrons, as electrons were absorbed in the South Atlantic Anomaly, not above the earthquake epicenters nor where NOAA detected them but having some hours of life after they were disturbed (see Fidani, 2020).

However, to consider electron burst L-shells around the L-shells corresponding to the earthquake epicenter projected at several altitudes constitutes an ambiguity in defining the phenomena that preceded earthquakes. So, it was shown that it is enough to select only electron bursts with L in a well-defined interval to guarantee that they correlate with strong earthquakes in West Pacific (see Fidani 2021). The validity of the new condition was confirmed by choosing electron bursts with the following: 1.21 ≤ L ≤ 1.31, pitch angles 56° ≤ α ≤ 74° and 108° ≤ α ≤ 126°, and positions −35° to 15° in latitudes and 230°−280° in longitudes. The optimization corresponded to the Δt = 1.5−3.5 h interval with the geographical distribution of correlated earthquakes depicted below.

The scenario representing a model of earthquake prediction based on these results needs to define volumes where earthquakes occur, where the target volume VT is 2-d space + 1-d time-space. In this volume, the points of earthquake occurrence can be identified, together with alarm volumes VA, as success (S) and failure of prediction (F) events that are earthquakes occurring inside or outside VA, respectively. In this case, a precursor volume VP containing the alarm events must be defined, which is generally different from VT; VP is the volume of the area where electron burst detection using NOAA satellites occurs, multiplied by the time of electron burst observations. An electron burst detection in VP is an alarm event that defines VA. With regard to the correlation mentioned above, for the Indonesian and Philippine latitudes and longitudes, VT is obtained by multiplying this area by the time spanned by the earthquake observations. In this scenario, the occurrence of an earthquake event is considered only with M above a magnitude threshold of 6.

The transfer entropy between the lithosphere and the ionosphere can be calculated as this is a complex system and information theory is able to describe non-linear interactions. The distribution in transfer entropy is shown below considering EQs, EBs, and the same time interval.

Peaks occurred for the same time delay as in the correlations, 1.5 to 3.5 h, and as well as for a new time delay, –􀀀58.5 to –􀀀56.5 h; this last is linked to EQ self correlations from the analysis (see Fidani, 2022).

A new statistical correlation analysis between precipitating EBs and strong EQs was carried out from the analysis of exactly 16.5 years of NOAA-15 particle data. This seemed 408 to indicate that electrons in the loss cone were mainly observed around 57 h before main shocks with M ≥ 6 in the East Pacific, comprising countries where seismic activity is frequently a danger. The new correlation again supports the hypothesis that there might exist a link between ionospheric and lithospheric activities of shallow EQs whose depths are less than 200 km. As for West Pacific EQs, also this correlation happens regardless of whether the EQs occurred in the sea or on the mainland (Fidani, 2022).