# Prerequisites Take a look at our other article about [[Variable Stars (Astro)|some of the general properties of variable stars]] before moving to this one! Also, check out [[M-Type Stars (Astro)|this article on red dwarves]]! # Intro: Magnets and the Star Red Dwarves are fully convective. Against all logic, these stars, actually the densest of any class of star, are dense enough so that convection's the best source for heat transfer. So treat a red dwarf as a very, very large fluid simulation - meaning that the magnetic fields of the star are very, very unstable! The sun, with its magnetic field, already causes **Coronal Mass Ejections** - ejections of ionising plasma aimed at any direction - and **Solar Flares**, a temporary brightening of the star as magnetic fields cut, break and intertwine. In other spots, these magnetic fields lead to a creation of What keeps these flares in check is that not all the material in the sun is convective - instead, the radiation pressure from within the star is high enough to prevent convection closer to the core, leading to an extremely dense *radiative zone*. For our fully-convective red dwarves, their magnetic fields are therefore amplified several times - being a big ball of moving ions, these stars can reach brightnesses of over thousands of times their usual. That's just one way magnetic fields can affect stars - the milder version of this, for the tamer red dwarf, is known as a **BY Draconis Variable**, where only the effects of sunspots on the star's surface give it the appearance of a variable star. # The Actual BY Drac Variable # Sources 1. https://lweb.cfa.harvard.edu/sdu/bydra.html