How to keep player momentum after a jump landing (2D)

Hey guys,

I'm creating a Mario clone and I need to keep the player's momentum into the jump and then onward into the landing. I can't figure out how to achieve this. Every time I land, the player has to build up momentum again. Any Idea how to fix this? Here's my code:

     Animator animator;
     Rigidbody2D rb;
     bool isGrounded;
     public float moveSpeed;
     public Vector2 acceleration;
     public float jumpHeight;
     public Transform groundCheckM;
     public Transform groundCheckL;
     public Transform groundCheckR;
 
     void Start()
     {
         animator = GetComponent<Animator>();
         rb = GetComponent<Rigidbody2D>();
         transform.eulerAngles = new Vector3(0, 0, 0);
     }
 
     private void Update()
     {
 
        if
              ((Physics2D.Linecast(transform.position,groundCheckM.position, 1 << LayerMask.NameToLayer("Floor/Platforms"))) || //Check if grounded
              (Physics2D.Linecast(transform.position, groundCheckL.position, 1 << LayerMask.NameToLayer("Floor/Platforms"))) ||
              (Physics2D.Linecast(transform.position, groundCheckR.position, 1 << LayerMask.NameToLayer("Floor/Platforms"))))
         {
             isGrounded = true;
             animator.SetBool("Jump", false);
         }
            
        else
         {
             isGrounded = false;
         } 
 
         animator.SetFloat("Walk", rb.velocity.x);  //Set animation float to x velocity 
        
         if (rb.velocity.x <= 0.03f && rb.velocity.x >= -0.03f && isGrounded) //Play "Idle" animation 
         {
             animator.Play("Mario_Idle");
         }
 
         if (rb.velocity.x >=4 || rb.velocity.x <=-4)
 
         {
             animator.speed = Mathf.Abs(rb.velocity.x / 5.5f); //Increase speed of walking animation with player's walking speed 
         }
 
     }
     void FixedUpdate()
     {
 
         if (Input.GetKey("d") || Input.GetKey("right")) //Move player to the right 
         {
             rb.AddForce(acceleration * rb.mass);
             transform.rotation = Quaternion.Euler (0, 0, 0);
         }
 
         else if (Input.GetKey("a") || Input.GetKey("left")) //Move player to the left
         {
             rb.AddForce(-acceleration * rb.mass);
             transform.rotation = Quaternion.Euler(0, 180, 0);
         }
 
             if (rb.velocity.x >= 10)
             {
                 rb.velocity = new Vector2(10, rb.velocity.y);   //Cap player speed at 10 when moving right
             }
 
         else if (rb.velocity.x <= -10)
             {
                 rb.velocity = new Vector2(-10, rb.velocity.y);  //Cap player speed at 10 when moving left 
         }
 
 
         if (Input.GetKey("space") && isGrounded) //Player jump 
         {
             rb.velocity += new Vector2(rb.velocity.x, jumpHeight);
             animator.SetBool("Jump", true);
         }
 
     }
 
 }