| Compiled by David (mrloferlofer) - The previous Solar Sector Boundary Crossing was on January 21, 2014: "SOLAR SECTOR BOUNDARY CROSSING: High-latitude auroras are possible on Jan. 21st when Earth crosses through a fold in the heliospheric current sheet. This is called a "solar sector boundary crossing," and NOAA forecasters estimate a 25% chance of polar geomagnetic storms when it occurs." |  Source: Dr. Tony Phillips 'Time Machine' Site Archive. |
According to NOAA's Forecast Discussion on February 2nd, 2014, published at 00:30 UTC & 12:30 UTC, a Solar Sector Boundary Crossing occurred the morning of February 1st @ 10:00 UTC:
"Around 1/1000 UTC a Solar Sector Boundary change from Away-to-Toward occurred ['+' is away from the Sun, '-' is toward the Sun is -]. The EPAM instrument indicated a slow rise in low energy particles, signalling the approach of the anticipated CME."
24-h Solar Wind Summary (@ 12:30 UTC): "Solar wind parameters were nominal with solar wind speed increasing slightly through the period from approximately 334 km/s to 380 km/s. Total field also saw a minor increase from 2 nT to 6 nT, while the Bz component was variable between +/-6 nT. Phi angle was mostly negative (towards) with minor deviations into a positive (away) sector."
Image adapted from Smith et al. "Along the plane of the Sun's magnetic equator, the oppositely directed open field lines run parallel to each other and are separated by a thin current sheet known as the "interplanetary current sheet" or "heliospheric current sheet" (see the figure above). The current sheet is tilted (because of an offset between the Sun's rotational and magnetic axes) and warped (because of a quadrupole moment in the solar magnetic field) and thus has a wavy, "ballerina skirt"-like structure as it extends into interplanetary space (see the figure on the left).
Because the Earth is located sometimes above and sometimes below the rotating current sheet, it experiences regular, periodic changes in the polarity of the IMF. These periods of alternating positive (away from the Sun) and negative (toward the Sun) polarity are known as magnetic sectors." - Interplanetary Magnetic Field (IMF).
Because the Earth is located sometimes above and sometimes below the rotating current sheet, it experiences regular, periodic changes in the polarity of the IMF. These periods of alternating positive (away from the Sun) and negative (toward the Sun) polarity are known as magnetic sectors." - Interplanetary Magnetic Field (IMF).
Research Paper Notes, Conclusions on Solar Sector Boundary Crossings:
"As the solar wind flows away from the Sun, the IMF is carried with it and has a spiral shape. Along the ecliptic plane, the IMF generally has 2 or 4 sectors per solar rotation (27 days) where it is pointed toward or away from the Sun. The surface separating the polarities is called the heliospheric current sheet. A sector boundary crossing occurs when the polarity of the IMF reverses. A well-defined sector boundary crossing has a uniform field direction for about 4 days before and after the crossing." - 'Effects Associated with the Sector Boundary Crossing on July 8, 1966.'
"It is concluded that Cosmic Ray density is high near the sector boundary. The decrease of neutron intensities after the boundary passage seem to be due to Forbush decreases which occur often after the boundary passages. The dominant part of cosmic ray density around the boundary correlates with solar wind velocity, irrespectively of the sense of IMF polarity change, and the increment per the change of solar wind velocity is consistent with the rate of 0.5% decrease per 100 km/s change derived by Lucci et al. (1979) and Munakata et al. (1979)." - 'IMF Sector Boundary and Cosmic Ray Intensity Variations.'
"Recent theoretical studies have shown that perturbations in the zonal equatorial electric field may be caused during conditions of enhanced geomagnetic activity by (a) a direct penetration of high latitude electric field associated with changes in the magnetospheric convection or changes in auroral or ring current systems (e.g., regs. 26-28) and (b) delayed changes in the atmospheric dynamo associated with large-scale perturbations in the thermospehric circulation owning to energy input to the high latitude thermosphere (29, 30).
The magnitude and direction of the perturbation electric field depend on a variety of conditions and the can enhance, oppose, or even reverse the normal equatorial electric field...All that can be inferred is that, on the average, westward (negative) perturbation electric fields prevail in the equatorial regions during the post-sunset period in wake of sector boundary passage owing to enhanced geomagnetic activity." - 'Response of the equatorial ionosphere to solar magnetic sector crossing.'
We can typically expect 2 to 4 Solar Sector Boundary Crossings per every 27 day Solar Rotation period. Solar Sector Boundaries are marked by a change in polarity of the Interplanetary Magnetic Field from positive (away from the Sun) and negative (towards the Sun). A list of Solar Sector Boundary crossings back from 1926 to the present exists over at Stanford's Wilcox Observatory Website.
Description from Leif Svalgaard: "The last two numbers are the number of days of each polarity on each side of the boundary, so "+,- 2014 01 10 18 9" means that there are 18 '+' days before the boundary and 9 '-' days after. This is to make it easy to do analysis, e.g. isolated SBs."
Ben (S0) recently commented about the rare, phenomenal explosion of auroras to start 2014, and especially the outburst visible at the beginning of February: "Earth's magnetic field has been slowly weakening since the 1600s, but recently has begun to rapidly decrease in strength, as much as 15%, according to NASA and the ESA. It is possible that the increased geomagnetic activity is a result of our weakening magnetic shield, and that it may continue to surprise us."
Description from Leif Svalgaard: "The last two numbers are the number of days of each polarity on each side of the boundary, so "+,- 2014 01 10 18 9" means that there are 18 '+' days before the boundary and 9 '-' days after. This is to make it easy to do analysis, e.g. isolated SBs."
Ben (S0) recently commented about the rare, phenomenal explosion of auroras to start 2014, and especially the outburst visible at the beginning of February: "Earth's magnetic field has been slowly weakening since the 1600s, but recently has begun to rapidly decrease in strength, as much as 15%, according to NASA and the ESA. It is possible that the increased geomagnetic activity is a result of our weakening magnetic shield, and that it may continue to surprise us."
Don't forget to check out Hour 1 & 2 of Red Ice Radio's Interview with Ben (S0):
| January 29th, 2014 - "We'll discuss the variable sun, its effects on earth and climate change. Ben elaborates on the connection between space weather, the natural environment and human condition. In the second hour, we discuss earthquakes, volcanoes and comets. How can we prepare for possible catastrophic changes on the horizon? Later, Ben talks about consciousness and placebo effect..." | |
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