At www.spaceweather.com (Sept 15th 2016) … there is an upcoming harvest moon this weekend which will be accompanied by a shadow on the moon, the result of a 'pencumbral lunar eclipse' – and we actually have a computer animation of the area affected (go to http://shadowandsubstance.com)
We also learn that earth's magnetic field can sometimes ring like a bell. Research by Rob Stammes, situated on the Lofoten Islands in Norway, has detected the strength and direction of the local magnetic field – as well as electrical current running through the ground. During a recent geomagnetic storm his recordings went haywire – they began ringing like a bell (rather, what is known as sinusoidal pulsations). These are natural low frequency oscillations and the physics is similar to anyone that has studies bells (hence the pun) or resonant cavities. Earth's magnetic field carves out a cavity in the surrounding solar wind but pressure fluctuations in the solar wind excite wave modes in the cavity. This phenomenon occurred at the same time as bright aurora.
Rob Stammes adds that he has been observing magnetic pulses in Norway for years. They seem to occur most often around the equinoxes. Interesting, as we are now approaching the autumnal equinox.