To those not inclined, enthusiastic gushing over Earth poised to cross a fold in the heliospheric current sheet on April 29/30 likely falls flat. That’s OK, twenty years ago I wouldn’t have understood a solar sector boundary crossing meant geomagnetic storm. Living in a state of gob smacked wonder over auroras, didn’t equate to comprehending how or why – shreds of murky high school science were of little use. Solar dynamic’s light didn’t flicker until the day I decided to figure it out from the perspective of one without a formal science education.
In October 2014 I wrote a post titled “Solar Sector Boundary Crossing”. If I do say so myself – a concise, accessible, easily understood window to the wonder of solar dynamics.
“Hang on for a lesson in solar dynamics – Earth is experiencing a solar sector boundary crossing. Let me explain….
The sun produces wind (currently 410.9 Km/second) that blasts across the cosmos. Just like Earth, our Sun has a magnetic field – known as the interplanetary magnetic field (IMF). Whipped into a spiral rotation, wind driven IMF rotates in one direction. It divides into spiral sections pointing to and away from the sun along the ecliptic plane ( a direct line between Earth and the Sun). The edge of this swirling mass has a surface separating polarities of planetary and solar magnetism called the heliosphere current sheet.
Earth’s magnetic field points north at the magnetopause (the point of contact between our magnetosphere and the IMF). If the IMF happens to point south at contact (scientific term, southward Bz) the two fields link causing partial cancellation of Earth’s magnetic field – in other words, opening a temporary door for solar energy to enter our atmosphere. Welcome solar sector boundary crossing – a phenomenon born of high solar wind and coronal mass ejections (CME’s – aka solar flares).
It takes 3 or 4 days for magnetism to sort itself out – in the meantime, and barring the occasional high frequency radio disruption, wonky GPS and cell phones, peppered with sudden power grid failure events – we’re treated to kick ass auroras.”