Parker Spiral:
The heliospheric current sheet, or interplanetary current sheet, is a surface separating regions of the heliosphere where the interplanetary magnetic field points toward and away from the Sun. A small electrical current with a current density of about 10−10 A/m2 flows within this surface, forming a current sheet confined to this surface. The shape of the current sheet results from the influence of the Sun’s rotating magnetic field on the plasma in the interplanetary medium. The thickness of the current sheet is about 10,000 km (6,200 mi) near the orbit of the Earth. [Wikipedia]
Accompanying the above is this cool depiction:
Noted on Spaceweather.com under the heading Sizzling Sunspot:
Any eruptions this weekend could have a strong effect on Earth. Sunspots located near the sun’s western limb are magnetically connected to our planet via the Parker Spiral. If AR3615 erupts while it is transiting this “danger zone,” energetic protons and electrons may be funneled back toward Earth for a solar radiation storm. Stay tuned!
