Collaborative Research: The Simpson Neutron Monitor Network

This three-year collaborative project is focused on building of a network of ground-based cosmic-ray monitors, called Neutron Monitors (NMs), operated by a consortium of three U.S. academic institutions, namely Universities of New Hampshire, Delaware and Wisconsin-River Falls. Invented by Prof. John Simpson in 1948, following his experience on the Manhattan Project, NMs have been used to detect and measure radiation in space, starting almost ten years before the space age.

They are stationed on the ground all over the globe, providing continuous measurements of cosmic radiation for over a half century. NMs measure the trends and changes in the radiation levels in space, which is critical information for travel by astronauts to the Moon and Mars. They can also detect intense, short-term bursts of radiation from the Sun that reach the ground.

All this activity is driven entirely by what the Sun is doing. NMs are robust and reliable and have assumed a new importance in recent years when used in conjunction with the international fleet of spacecraft and with neutron monitors in other countries. Now, all the NMs sponsored by the U.S. are being linked into what will be the Simpson Neutron Monitor Network, which will make it more efficient to coordinate operations and science.

During this three-year collaborative project, the consortium will carry out this research, teasing new information out of these heritage instruments and providing researchers around the world with up-to-date radiation climate data. Cosmic rays entering the Earth’s atmosphere are messengers informing us about large-scale heliosphere structure, local space environment and solar activity.

They have already passed through and interacted with the interplanetary magnetic field, and they carry information of its detailed structure. Some of these cosmic rays possess enough energy to reach the ground. A NM is a ground-based particle detector that records the nucleonic component in particle showers.

This directly correlates with the number of high energy cosmic rays striking the Earth’s atmosphere. The analysis of these data is used to build an understanding of the Sun’s influence on the Solar System. Because of the large detector volume exploited by ground-based stations, neutron monitors remain the state-of-the-art instrumentation for measuring rigidity >1GV cosmic rays.

The programmatic linking of these instruments run by the Universities of New Hampshire, Delaware and Wisconsin-River Falls will secure a continuity of quality data for the global community, as called out in the National Space Weather Plan and Congressional legislation. The data from these instruments are used by many, including, space weather predictors, industry, space scientists, homeland security and hydrologists.

The NM stations span a wide range of latitudes, from the South Pole to the Arctic regions. The contributors to the NM signal include cosmic rays from the galaxy that are heavily modulated by solar activity and from the Sun itself in the form of high energy bursts of protons. The variability of these agents reveals conditions in interplanetary space, general solar activity and the fundamental processes that produce cosmic rays throughout the Universe.

With today’s computing resources, we better understand how these instruments detect radiation, and the consortium will thus be able to extract new information from these workhorse devices. This will shed new light on how the distribution of cosmic rays varies with time, geography and particle energy. The consortium will study how to permanently secure the operations of the monitor network and intelligent ways of expanding the network to complement those at existing sites.

The education and outreach goals of the project include a research position for a postdoc, a wide variety of opportunities and experiences for undergraduates, as well as opportunities for high school and elementary school students. The research and EPO agenda of this collaborative project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.