What Happens if We Have No Magnetic Field Left at All? By Brian Simpson

     I have often laid awake a night thinking about things to worry about, so that I could call myself a chronic insomniac, but I have not, until now, worried about the Earth’s magnetic field disintegrating. Maybe it will not, but it does seem to be diminishing, causing big techy problems.
  https://news.sky.com/story/earths-magnetic-field-which-protects-us-from-solar-radiation-is-mysteriously-weakening-11992022

“Earth's magnetic field, which is vital to protecting life on our planet from solar radiation, is mysteriously weakening. On average the planet's magnetic field has lost almost 10% of its strength over the last two centuries, but there is a large localised region of weakness stretching from Africa to South America. Known as the South Atlantic Anomaly, the field strength in this area has rapidly shrunk over the past 50 years just as the area itself has grown and moved westward. Over the past five years a second centre of minimum intensity has developed southwest of Africa, which researchers believe indicates the anomaly could split into two separate cells. The anomaly is causing technical difficulties for satellites orbiting the Earth. European Space Agency (ESA) scientists from the Swarm Data, Innovation and Science Cluster (DISC) are using data from ESA's Swarm satellite constellation to study the anomaly. Swarm satellites are designed to identify and precisely measure the different magnetic signals that make up Earth's magnetic field. Dr Jurgen Matzka, from the German Research Centre for Geosciences, said: "The new, eastern minimum of the South Atlantic Anomaly has appeared over the last decade and in recent years is developing vigorously. "We are very lucky to have the Swarm satellites in orbit to investigate the development of the South Atlantic Anomaly. The challenge now is to understand the processes in Earth's core driving these changes." One speculation is that the weakening of the field is a sign that the Earth is heading for a pole reversal - in which the north and south magnetic poles flip. This flip doesn't happen immediately, but instead would occur over the course of a couple of centuries during which there would be multiple north and south magnetic poles all around the globe. "Such events have occurred many times throughout the planet's history," said ESA, noting "we are long overdue by the average rate at which these reversals take place (roughly every 250,000 years)".

     So, maybe we are heading towards a north south pole reversal, but the above article says not to worry as we won’t be here when it happens.
  https://www.nationalgeographic.com/news/2018/01/earth-magnetic-field-flip-north-south-poles-science/

     But, search more and we can find a figure of about two centuries for the reversal, with a decay over that period:
  https://earthsky.org/earth/study-magnetic-field-reversals-happen-faster-than-thought
  https://www.pnas.org/content/115/36/8913

     Thus, there could be a significant reduction in the protection offered by the magnetic field this century, with the South Atlantic Anomaly expanding even faster. That means that high tech society will face a major threat from EMP solar events, that have a significant probability of a new Carrington event each year. It is thus not improbable that it could be “lights out” at some point, given how slow the world is moving to protect the electric infrastructure from solar events. So, there is something new to worry about at bed time after all!
  https://www.space.com/43173-earth-magnetic-field-flips-when.html
  https://www.livescience.com/earth-magnetic-field.html
  https://www.ibtimes.com/earths-magnetic-field-weakening-could-collapse-eventually-expert-warns-2892091