To day is September 11, 2008.Just 7 years ago onSeptember 11, 2001,around 8h45m ET…
Atlantic Hurricanes, Geomagnetic Disturbances and Cosmic Ray Intensity Changes. S. Kavlakov Bulgarian Academy of Sciences (firstname.lastname@example.org)
As it is well known that the hurricanes are high velocity circular winds born over the hot equatorial waters of the oceans. Their whole vortex generally spread out to gigantic rings with a diameter of: several hundredkilometers. The energy accumulated during these processes is enormous. It could be compared with the energy of explosion of: more than thousand Hiroshimatype atomic bombs.
That enormous energy explains the vast disasters produced by the hurricanes, when they touch a populated area.
After Katrina - August 2005:Hundreds were killed, more than a hundred thousand were left homeless.
After Katrina - August 2005:…and that remained from the South suburb of New Orleans.
That also added to our interest for a detailed study of a possible similar parallel between the appearance and development of the hurricanes from one side and the geomagnetic disturbances and Cosmic Ray intensity from the other. Finding even slight statistically significant interconnection between them could surely help a better hurricane early predictions and safe a lot of human lives.
Lately, the question if several purely meteorological processes of the terrestrial atmosphere are connected with the magnetosphere disturbances, CR intensity changes, and solar activity has been largely discussed: (Kudela and Storini, 2005), (Marsh et al. 2000), (Svensmark 1998) and many others.
In some of our earlier works a significant statistical relationship has been found between geomagnetic activity as measured by the KP index and hurricane intensity as measured by the maximum wind speed. Persistent appearances of sharp CR intensity changes before the starts of some hurricanes have been also observed.
For our work, presented here, we used the following data: • All 6 hours hurricane data recorded in the 55 years interval 1951-2005. [80665 data] • All 3 hours Geomagnetic Kpindexes recorded in the same 55 years long interval [160704 data]. • All 1 hourCR data measured continuously 55years with the Neutron Monitor of [482136 data]. Climax high mountain station: 39.37N; 106.18W; alt. 3400 m. 2.97 GeV cut-off rigidity.
Now: • Instead of hurricane rotational wind velocity W used earlier, now we use its first derivative dW/dt, assuming that it is directly connected with the hurricane energy intensification.
We found a persistent presence of at least one Forbush Decrease event (FE), in the time interval of about 3 to 16 days before the start of considerable number of hurricanes. A sharp rise in the geomagnetic parameters KP was also noticed in the time intervals preceding the star of many hurricanes. All that is centered around the hurricane starts (yellow triangles).
On the previous slides, four powerful hurricanes are presented to illustrate that. There: the hurricane rotational velocity (W-red line) and its derivative (dW/dt-blue line) are overlapped on the daily changes of the Kp geomagnetic index (black bars). Arbitrary units are used.
But, sorry, it is difficult to find even an relatively stable average time difference between the starts of these events. Earlier we accepted as basic points the start days of the hurricanesand made our calculations towards them.Here we chose another basic days:1. We defined as Kp”0” these days when the Kp index is 70% above the total 55 years average.2. We took as Forbush Event FE”0” these days when the sudden decrease of the CR intensity is below -3% from the local average. For these “0” days we take the corresponding hurricane intensification values [dW/dt].
Trying to find a interconnection between the hurricane intensification (dW/dt) and the appearance of High KP or FE, we divided all our hurricane hours in two parts: 1. Over a vast area of hot waters (shown as white rectangle on the map), where the intensification comes mainly from the vertical streams powered by the high surface temperature. 2. And over the whole remained, area, with relatively low water surface temperature and near to land. There we could expect a moderate influence of the powerful atmospheric factors and probably more noticeable influence of the geomagnetic factors.
As it could be expected: the intensification over the hot ocean waters is about 10 times more powerful than over the other oceanic areas. [0.313 kt/hour toward 0.0342kt/hour] • Over hot waters the intensification increases around the corresponding “0” days are smaller. [73% toward 108% for Kp, and 16% toward 60% for FE ]. • We assume that there is a possibility to accept a small participation of some unknown mechanism, connected with the geomagnetic factors to the intensification process. • Naturally, over hot water the main intensification process is very powerful, so the influence of this mechanism is reduced. The statistical significance was estimated by means of “bootstrap” procedure.
Overlapping the hurricane intensifications dW/dt for Kp”0” and for FE”0” days, as well as six days before them and six days after, we obtained these graphs. Only three days (in bold red on the graphs) around the “0” day and the “0” day itself (the yellow triangle) were taken for our evaluations.
Conclusions. 1. • Over all the Atlantic the intensification dW/dt rise around KP and FE “0” days. • The rise is well expressed far from the hot oceanic waters • The intensification is larger AFTER the corresponding “0” day. • In the case of KP that rise is significant • In the case of FE the rise is minor and unstable. • But taking in account their persistent appearance before the hurricane start [depicted on the first graphs.] probably the FE contribution to the storm intensification is within a longer time range • Because of all that • and • because the large amount of investigated hurricanes • in an interval of more than half a century, • we could permit ourselves to support the existence of • a slight geomagnetic influence on the hurricane energy.
Conclusions. 2. • The result is consistent with an earlier study in showing a connection between Kp values and hurricane intensity. It expands on the earlier work by focusing on intensification rather than intensity. • Along the lines of our earlier study we suggest that a possible physical mechanism is related to increased ionization of the upper extent of the tropical cyclone vortex leading to increased condensation and additional warmth throughout the column. Obviously more work is needed to better understand this interesting result.