Abstract: This Report Presents The Result Of The Measurement Of Characteristic Times For Relativistic Solar Energetic Par- Ticle Events Observed By Neutron Monitors. The Typical Profile Of A Solar Event Observed By Neutrons Monitors Is A Fast Rise And A Slow Decay. But These Times Differ Between Events (From A Few Minutes To Several Hours) And Quantifying Them Is Interesting. In Fact, Studying These Characteristic Times Allows Us To Better Understand Solar High Energy Events. For This, We Used The Neutron Monitor Database (Nmdb) [1] And Python To Compute The Rise Time And The Decay Time. We Observed That There Is A Linear Relationship Between Rise Time And Decay Time Of These Solar Events.there Are Some Possible Interpretations For These Characteristic Times. These Times May Be Related To The Dura- Tion Of Particle Acceleration Or The Propagation Of The Particles In The Interplanetary Medium. We Looked Then For A Link Between The Measurement Of Neutron Monitors At The Earth And The Solar Activity: In X-rays, And The Microwave Domain. Furthermore, We Studied The Fluctuations Of The Interplanetary Magnetic Field. However, All These Attempts Were Unsuccessful To Find A Relation With The Rise Time Measured By Neutron Monitors. But Ejection Speeds Of Coronal Mass Ejections And Rise Time Solar Events Detected By Neutron Monitors May Be Linked.